Chlorination of hydrocarbons

ABSTRACT

A process for the chlorination of hydrocarbons wherein the production of the chlorinated hydrocarbon is accelerated by carrying out such chlorination in the presence of sodium sulfide. The presence of sodium sulfide leads to the production of the chlorinated hydrocarbon, hydrogen sulfide, and sodium chloride as products. The sodium sulfide is preferably that produced in the desulfurization of petroleum fractions utilizing metallic sodium. This application is a continuation-in-part of application Ser. No. 735,397, filed June 7, 1968, now U.S. Pat. No. 365792. The present invention is directed to the improved process for the chlorination of hydrocarbons; more particularly, the present invention is directed to an improved process for the chlorination of aliphatic and aromatic hydrocarbons wherein such chlorination is carried out in the presence of sodium sulfide. Various processes are known for the chlorination of hydrocarbons, specifically aliphatic and aromatic hydrocarbons so as to produce a mono- and di-chlorinated product. Most of these processes involve the reaction of chlorine with the aliphatic or aromatic hydrocarbon. While various catalysts have been known for accelerating amd promoting of the chlorination reaction, many processes developed heretofore have been found to have various deficiencies. In this regard, for example, acceleration of the chlorination reaction to a point of maximum conversion to the mono- or di-chlorinated hydrocarbon has always been lacking. In accordance with the present invention, however, a process has been discovered whereby it is possible to chlorinate aliphatic and aromatic hydrocarbons so as to produce the mono- and di-chlorinated product in a manner eliminating the various drawbacks of previously developed processes. Such improvements in accordance with the present invention involve carrying out the chlorination of an aliphatic or aromatic hydrocarbon with chlorine at a temperature of from about 20* to 150*C. wherein the process is conducted in the presence of sodium sulfide. It is hypothesized in accordance with the present invention that the presence of sodium sulfide in the chlorination reaction accelerates and promotes the production of the chlorinated hydrocarbon by providing for the production of stable products in addition thereto, i.e., sodium chloride and hydrogen sulfide. In this way the reaction is accelerated toward the production of the desired mono- or di-chlorinated hydrocarbon. Accordingly, it is a principle object of the present invention to provide a process for the chlorination of hydrocarbons wherein such process eliminates the inherent disadvantages and deficiencies of heretofore proposed processes. It is a further object of the present invention to provide such a process for the chlorination of hydrocarbons wherein such process is improved by the presence of sodium sulfide in the chlorination reaction. A still further object of the present invention relates to the process for the chlorination of aliphatic and aromatic hydrocarbons with chlorine at a temperature of 20* to 150*C., such process being characterized by the presence of sodium sulfide. Yet a further object of the present invention relates to an improved process for the chlorination of aliphatic anD aromatic hydrocarbons with chlorine wherein such process is carried out in the presence of sodium sulfide derived from the desulfurization of petroleum factions with metallic sodium. Still further objects and advantages of the novel process of the present invention will become more apparent from the following, more detailed description thereof. The foregoing objects and advantages of the present invention are achieved by carrying out the chlorination of hydrocarbons, e.g., aliphatic or aromatic hydrocarbons, in the presence of sodium sulfide. Thus, for example, the process of the present invention can be described by the following equation:

0 iJmied Siaies P000190 1 1 1111 3,760,014 Piaskett 14 -1 Sepi. 18, 1973 [5 CHLORINATION 01F HYDROCARBONS 2,849,501 8/1958 Bolton 260 650 R 1,741,305 12/1929 Jaeger..... [751 Barry Hash, Gem, 3,226,447 12/1965 Bing et a1 260/650 R Swltzerland FOREIGN PATENTS OR APPLICATIONS [73] Ass'gnee' Mamn washmgton 988,306 4/1965 Great Britain 260/650 R 223,024 7/1959 Australia 260/650 R [22] Filed: Feb. 22, 1971 21 A L N 5 117,382 Primary Examiner-Howard T. Mars 1 pp 0 Attorney-Sherman & Shalloway Related US. Application Data [63] Continuation-impart of Ser. No. 735,397, June 7, [57] ABSTRACT 1968, Pat. NO. 3,565,792.

A process for the chlormauon of hydrocarbons wherem 5 s Cl 260/650 R, 204/63, 423/563, the production of the chlorinated hydrocarbon is accel- 423/574, 260/660 erated by carrying out such chlorination in the pres- 51 1m. (:1. (3076 25/06, C070 25/03 We of sodium Sulfide The Presence of sodium Sulfide 5s 1 Field of Search 260/650 R; 23/205 leads to the Production of the chlorinated hydrocarbon, hydrogen sulfide, and sodium chloride as prod- [56] References Cited dots. The sodium sulfide is preferably that produced in UNITED STATES PATENTS the desulfurization of petroleum fractions utilizing met 11' d' 2,976,330 3/1961 Guerin 260/650 R a lc so mm 3 Claims, 1 Drawing Figure CHLORHNATHON 01F HYDROCARBONS This application is a continuation-in-part of application Ser. No. 735,397, filed June 7, 1968, now US. Pat. No. 365792.

The present invention is directed to the improved process for the chlorination of hydrocarbons; more particularly, the present invention is directed to an improved process for the chlorination of aliphatic and aromatic hydrocarbons wherein such chlorination is carried out in the presence of sodium sulfide.

Various processes are known for the chlorination of hydrocarbons, specifically aliphatic and aromatic hydrocarbons so as to produce a monoand dichlo'rinated product. Most of these processes involve the reaction of chlorine with the aliphatic or aromatic hydrocarbon.

While various catalysts have been known for accelerating amd promoting of the chlorination reaction, many processes developed heretofore have been found to have various deficiencies. In this regard, for example, acceleration of the chlorination reaction to a point of maximum conversion to the monoor di-chlorinated hydrocarbon has always been lacking. In accordance with the present invention, however, a process has been discovered whereby it is possible to chlorinate aliphatic and aromatic hydrocarbons so as to produce the monoand di-chlorinated product in a manner eliminating the various drawbacks of previously developed processes.

Such improvements in accordance with the present invention involve carrying out the chlorination of an aliphatic or aromatic hydrocarbon with chlorine at a temperature of from about to 150C. wherein the process is conducted in the presence of sodium sulfide. It is hypothesized in accordance with the present invention that the presence of sodium sulfide in the chlorination reaction accelerates and promotes the production of the chlorinated hydrocarbon by providing for the production of stable products in addition thereto, i.e., sodium chloride and hydrogen sulfide. In this way the reaction is accelerated toward the production of the desired monoor di-chlorinated hydrocarbon.

Accordingly, it is a principle object of the present invention to provide a process for the chlorination of hydrocarbons wherein such process eliminates the inherent disadvantages and deficiencies of heretofore proposed processes.

lt is a further object of the present invention to provide such a process for the chlorination of hydrocarbons wherein such process is improved by the presence of sodium sulfide in the chlorination reaction.

A still further object of the present invention relates to the process for the chlorination of aliphatic and aromatic hydrocarbons with chlorine at a temperature of 20 to 150C, such process being characterized by the presence of sodium sulfide.

Yet a further object of the present invention relates to an improved process for the chlorination of aliphatic and aromatic hydrocarbons with chlorine wherein such process is carried out in the presence of sodium sulfide of hydrocarbons, e.g., aliphatic or aromatic hydrocarbons, in the presence of sodium sulfide. Thus, for example, the process of the present invention can be described by the following equation:

2 RH 2 Cl Na s 2 NaCl H S 2 R-Cl wherein R represents an aliphatic or aromatic hydrocarbon group.

It can be seen from the foregoing that through the process of the present invention, involving the presence of sodium sulfide in the chlorination process, stable products including sodium chloride and hydrogen sulfide as well as the desired chlorinated hydrocarbons are produced. Accordingly, it is hypothosized that the production of such stable products through the presence of sodium sulfide is that which allows for the acceleration of the chlorination reaction. Accordingly, pursuant to the process of the present invention, high yields of high purity chlorinated hydrocarbons can be obtained.

The chlorination reaction of the present invention, wherein the same is conducted in the presence of sodium sulfide, is generally conducted at a temperature of 20 to 150C.

In accordance with the present invention, while the amount of sodium sulfide present in the reaction system is generally not critical to carrying out the advantageous chlorination reaction, it is preferable that the sodium sulfide be present in an amount stoichiometrically derived from the desulfurization of petroleum factions with metallic sodium.

Still further objects and advantages of the novel process of the present invention will become more apparent from the following, more detailed description thereof.

The foregoing objects and advantages of the present invention are achieved by carrying out the chlorination equivalent to that amount required in the chlorination reaction in accordance with the foregoing equation. For example, in the production of a mono-chlorinated hydrocarbon product, the sodium sulfide need be present in the reaction system only in an amount of approximately 1 mol per two mols of hydrocarbon and two mols of chlorine. In accordance with the foregoing equation, such a reaction system yields two mols of the mono-chlorinated hydrocarbon product, 1 mol of hydrogen sulfide, and two mols of sodium chloride. Such reaction in accordance with the present invention can be carried out with an efficiency of from about to 85 percent conversion per pass.

In addition, in the production of a di-chlorinated hydrocarbon product, the sodium sulfide .is generally employed in an amount of approximately 1 mol per 1 mol of hydrocarbon and two mols of chlorine. Such a reaction system is capable of yielding 1 mol of the dichlorinated hydrocarbon product, 1 mol of hydrogen sulfide, and two mols of sodium chloride. Such reaction generally occurs with an efficiency of 45 to percent conversion per pass.

While the amount of sodium sulfide need only be that which is stoichiometrically equivalent, based upon the desired reaction and reaction products, it is quite obvious that an excess of sodium sulfide does not in any way interfer with the reaction but rather would also tend to lead the reaction to completion. Accordingly, there is no upper limit to the amount of sodium sulfide which may be present in the reaction system, except one of economics. in accordance with the present invention, however, it is preferred that the amount of sodium sulfide present in the reaction system be approximately 1 to 5 mols per mol of hydrocarbon. Within these limits, very effective chlorination of the hydrocarbon can be conducted.

The process of the present invention can be conducted with regard to the chlorination of any and all hydrocarbons which are conventionally chlorinated with chlorine. in this regard, the process of the present invention comprises an improvement in such typical chlorination reactions.

Thus, for example, the hydrocarbon may be suitably selected from aliphatic hydrocarbons of two to fifteen carbon atoms and aromatic hydrocarbons of six to twelve carbon atoms. For example, suitable aliphatic hydrocarbons include such as:

ethane n-propane isopropane n-butane n-hexane n-octane isooctane n-decane n-dodecane, etc.

Similarly, suitable aromatic hydrocarbons include benzene and substituted benzenes wherein the substitution is selected from one or more lower alkyl groups. Such materials include, for example, toluene, xylene, ethylbenzenes, etc.

It should again be recognized that the foregoing aliphatic and aromatic hydrocarbons are only exemplary of those which can be utilized in the improved chlorination process of the present invention and any conventional hydrocarbon chlorinated with chlorine can be advantageously utilized.

It is quite obvious that various sources are available for the sodium sulfide utilized in the process of the present invention. While this is true, a very advantageous source for the sodium sulfide utilized in the chlorination reaction is a byproduct of the desulfurization of petroleum factions utilizing sodium metal. For example, copending application Ser. No. 735,397 describes a cyclic process for desulfurizing crude petroleum fractions, comprising contacting a cold crude petroleum fraction with a dispersion of sodium metal in a light bydrocarbon fraction under ambient temperature conditions; and thereafter separating the product of such desulfurization into a desulfurized crude petroleum fraction and a sodium sulfide precipitate. While copending application Ser. No. 735,397 goes on to describe the reaction of such precipitate with hydrogen chloride to obtain hydrogen sulfide and by-product sodium chloride which can be subsequently utilized as the electrolyte in an electrolytic cell for the production of fresh, molten sodium metal, the sodium sulfide which is obtained initially from the desulfurization reaction can be advantageously utilized in the chlorination reaction of the present invention. The sodium chloride thus formed can then be utilized as the electrolyte in an electrolytic cell for the production of molten sodium metal which; when dispersed in a light hydrocarbon fraction, can be employed for the desulfurization of new crude petroleum fractions so as to initiate the production of a desulfurized fraction and fresh sodium sulfide. Additionally, the electrolysis of molten sodium chloride provides gaseous chlorine as a product in addition to sodium metal, and the gaseous chlorine can be effectively used in the chlorination of further hydrocarbons.

Thus, the process of the present invention can, itself, form a cyclic process wherein sodium sulfide employed in the chlorination reaction is obtained through the desulfurization of crude petroleum fractions with sodium and the sodium chloride obtained as a by-product of the chlorination reaction can be utilized as the electrolyte in an electrolytic cell for the production of sodium metal. Accordingly, the disclosure set forth in copending application Ser. No. 735,397, relative to the desulfurization of crude petroleum fractions with sodium and the subsequent electrolysis of molten sodium chlorind is herein incorporated by reference.

lnaccordance with the present invention, it is prefered to convert the hydrogen sulfide, produced as a by-product, to elemental sulfur. This can be done by any conventional technique, although it is preferred in accordance with the present invention to pass the hydrogen sulfide gas generated during the chlorination reaction into a Claus reactor system where the hydrogen sulfide is combined with sulfur dioxide, preferably generated by burning a portion of the hydrogen sulfide with air, so as to produce water vapor and elemental, molten sulfur. The elemental, molten sulfur which is produced through such reaction is, of course, a valuable by-product of the process of the present invention.

The process of the present invention will now be further described by the reference to the accompanying FIGURE, which comprises a flow diagram illustrating the novel features of the instant process.

In the FIGURE, sodium sulfide, preferably formed during the desulfurization of crude petroleum fractions with metallic sodium, enters repulper 10 through line 12 wherein it is combined with the hydrocarbon to be chlorinated, entering repulper 10 through line 14. in repulper 10, a slurry is formed with the sodium sulfide and hydrocarbon, the slurry leaving repulper 10 through line 14.

The slurry of sodium sulfide and hydrocarbon leaving repulper 10 in the form of a slurry through line 14 enters a chlorination reactor 20 together with chlorine introduced through line 22. Chlorination reactor 20 is fitted with a suitable motor driven stirrer 24, capable of stirring the reactants sufficiently so as to effectively control the rate of the chlorination reaction.

In the chlorination reaction, the chlorine and hydrocarbon react to produce the monoor di-chlorinated' hydrocarbon, depending upon the molar ratio of chlorine to hydrocarbon and the sodium sulfide present provides for the production of sodium chloride and hydrogen sulfide by-products. As indicated previously, it is in this way that the presence of sodium sulfide accelerates the chlorination reaction through the production of stable by-products.

The sodium chloride formed during the chlorination reaction as a by-product precipitates out of the reaction system and is collected in the bottom portion 26 of chlorination reactor 20. The sodium chloride may be withdrawn from chlorination reactor 20 through valve 28 and may be passed through line 30 to a rotary filter 32 wherein the sodium chloride is dried to form a filter cake by elimination of any entrained liquor. The filter cake may then be passed through line 34 to the feed for an electrolytic cell wherein the sodium chloride is employed as the electrolyte. in this regard, the electrolytic cell employing sodium chloride as the electrolyte may comprise a Downs or Chlor-metals cell wherein fused salt such as sodium chloride is employed. In particular, the Chl'ormetals cell allows for the production of molten sodium in a very efficient manner utilizing a flowing molten lead cathode, the sodium metal which is formed being suitable for use in the desulfurization ofcrude petroleum fractions.

The liquor which is entrained in the sodium chloride and which is withdrawn from rotary filter 32 may be returned to the chlorination reactor 20 through line 36. As shown in the FIGURE, the entrained liquor is preferably passed into the slurry of hydrocarbon and sodium sulfide entering chlorination reactor 20 through line 14.

The other by-product of the chlorination reaction, i.e., hydrogen sulfide gas, is withdrawn from chlorination reactor 20 through line 38. Preferably, the hydrogen sulfide gas leaving chlorination reactor 20 through line 38 is passed to a reactor in which the hydrogen sulfide can be converted to elemental sulfur. As seen in the FIGURE, the hydrogen sulfide gas in line 38 is preferably passed to a Claus reactor 40 in which the hydrogen sulfide gas reacts with sulfur dioxide introduced through line 42. The sulfur dioxide is preferably obtained by burning a portion of the hydrogen sulfide with air. The sulfur dioxide combines with the hydrogen sulfide in Claus reactor 40 to produce water vapor which exits through line 44 and elemental molten sulfur which exits through line 46.

As indicated above, the example of the Claus reactor wherein hydrogen sulfide is reacted with sulfur dioxide to produce water vapor and elemental sulfur is only one well known process allowing for the effective conversion of hydrogen sulfide to a more useful product. In this connection, other well known processes can be advantageously adopted instead of the Claus reactor, including for example, the well known contact sulfuric acid process wherein the hydrogen sulfide is oxidized to sulfur dioxide and thereafter to sulfur dioxide to be reacted with water vapor in the production of sulfuric acid. Accordingly, the illustration of the Claus reactor is only exemplary in accordance with the process of the present invention and the same is not in any way to be deemed limited thereto.

As seen in the FIGURE, chlorinated hydrocarbon and unreacted hydrocarbon exit from chlorination reactor 20 through line 48 and the chlorinated hydrocarbon and unreacted hydrocarbon enter fractionation tower 50. Fractionation tower 50 is employed to separate the chlorinated hydrocarbon fraction from the unreacted hydrocarbon fraction by distillation. Thus, with the proper application of heat, the chlorinated hydrocarbon can be separated in fractionation tower 50 from the unreacted hydrocarbon by distillation overhead, exiting fractionation tower 50 as vapor through line 52 into a water cooled condenser 54. In the water cooled condenser 54, the hydrocarbon overhead is condensed to liquid hydrocarbon and is withdrawn from condenser 54 through line 56 where it is split into reflux to be turned to fraction tower 50 through line 58 with the balance of the stream being recycled to line 14 containing entering hydrocarbon for repulper through line 60. The chlorinated hydrocarbon leaves fractionation tower 50 through line 62. The chlorinated hydrocarbon can then be passed to stations, notshown, for washing with caustic to remove traces of hydrochloric acid and dissolved hydrogen sulfide.

In connection with fractionation tower 50, it should be quite obvious that the particular conditions thereof vary depending upon the materials to be fractionated. For example, the fractionation of benzene and dichlorbenzenes can be effectively carried out at a tower pressure of between I atmosphere and 10 atmospheres and a temperature not exceeding lC. in the tower bot tom, but exceeding lO0C. in the top of the tower. The number of theoretical trays required in the tower for the fractionation and the associated recycle/reflux ratio through lines 58 and 60 can be easily determined based upon the desired degree of purity in the bottoms product and overhead condensed vapor. It should be quite apparent that the particular temperature, pressure, and number of trays for any particular hydrocarbon/chlorhydrocarbon system can be easily determined by one skilled in the art.

The process of the present invention is particularly adapted for the chlorination of benzene wherein chlorbenzene or dichlorbenzene is produced utilizing sodium sulfide to accelerate the reaction. For example, the chlorination of benzene to produce chlorbenzene can be effectively carried out at a temperature of from about 40 to 50C. in accordance with the present invention while the production of dichlorbenzene can suitably be conducted at a temperature of 60 to 70C. Here again, the amount of sodium sulfide needed to accelerate the chlorination reaction depends upon the nature of the starting materials and the desired product. A stoichiometrically equivalent or greater amount, however, will effectively produce the advantageous results of the present invention.

The process of the present invention has the following advantages over conventional chlorination processes:

l. a cyclic process can be provided through the use of sodium sulfide derived from the desulfurization of hydrocarbon fractions using metallic sodium. The metallic sodium used for such desulfurization can be regenerated in accordance with the present invention by employing the sodium chloride obtained as a byproduct of the chlorination reaction as the electrolyte in an electrolytic cell. 2. The chlorination reaction wherein an aliphatic or aromatic hydrocarbon is chlorinated with chlorine is accelerated through the production of stable by-products, e.g., sodium chloride and hydrogen sulfide, through the presence of sodium sulfide within the chlorination reaction.

3. Due to the cyclic nature of the process, stable products and by-products are produced and utilized with greatest efficiency, thereby allowing the process to be economically advantageous.

The present invention will now be described by reference to the following examples. It. should be understood that such examples are presented for purposes of illustration only and the present invention is in no way to be deemed as limited thereto.

EXAMPLE 1 Sodium sulfide, to be used in a chlorination reaction in accordance with the present invention, is produced as follows. A crude Pennsylvania oil which had not been previously refined for the elimination of any contaminants or the removal of any undesirable constituents is contacted for a period of one minute at ambient temperatures with a dispersion of sodium metal in butane, the sodium content of such dispersion being approximately 30 percent by weight. The dispersion of sodium metal and raw crude oil are introduced continuously into a contactor with agitation so that the dispersion at all times corresponds to approximately 5 percent by weight of the contents of the contactor. The

contents of the contactor are continuously withdrawn and delivered to a centrifuge which provides a desulfurized liquor for further crude oil distillation and fractionation and a precipitate containing sodium sulfide. This precipitate of sodium sulfide is used in the chlorination reaction.

Utilizing the system such as illustrated in the accompanying FIGURE, the sodium sulfide produced above is passed into a repulper wherein a slurry of the sodium sulfide in benzene is produced. Benzene is fed to the repulper in such an amount as to be present in a molar ratio of about 1:1 with regard to the entering sodium sulfide.

The sodium sulfide/benzene slurry is passed to a chlorination reactor wherein chlorine is introduced at a rate so as to effect reaction of about two moles of chlorine per mole of benzene. The chlorination reactor is kept at a reaction temperature of 60 to 70C. with constant stirring.

As a result of the chlorination reaction, hydrogen sulfide gas is taken off overhead from the chlorination reactor and sodium chloride precipitates and is drawn from the bottom of the reactor. A reaction mixture of dichlorbenzene and unreacted benzene is drawn off from the middle of the reactor, the benzene being converted to dichlorbenzene at a rate of approximately 65 to 70 percent conversion. The mixture of dichlorbenzene and benzene is introduced into a fractionation tower below the middle, the temperature at the bottom of the tower being approximately 165C. with that at the top being approximately 110C. Utilizing such a fractionation tower, almost complete separation of the dichlorbenzene/benzene mixture occurs with the benzene being withdrawn overhead and condensed and the desired dichlorbenzene being withdrawn at the bottom. The dichlorbenzene product is thereafter treated in the conventional manner with caustic to remove any entrained hydrogen chloride or hydrogen sulfide.

In a manner similar to that described previously, the hydrogen sulfide gas which is produced as a by-product is passed to a Claus reactor wherein the same is reacted with sulfur dioxide derived by burning a portion of the hydrogen sulfide gas so as to produce elemental, molten sulfur and water vapor. Similarly, the sodium chloride is melted and used as the molten electrolyte in a Chlormetals electrolytic cell employing a molten lead cathode. The electrolysis of the molten sodium chloride in the electrolytic cell provides a stream of molten sodium as a primary product with gaseous chlorine being evolved. The molten sodium is then ready for reuse as a dispersion in desulfurization of further crude oil while the chlorine evolved can be utilized for further chlorination of hydrocarbons.

EXAMPLE 2 Example I is repeated except that the chlorine is introduced into the reaction system at a rate so as to produce chlorbenzene as the principle product. The reaction vessel is maintained at a temperature of 40 to 50C. and the slurry of benzene/sodium sulfide is such that the benzene to sodium sulfide molar ratio is approximately 2:1.

As a result of such a reaction, a mixture of chlorbenzene and unreacted benzene is produced at a conversion of approximately to percent. The conditions of the fractionation tower are modified slightly so as to achieve ultimate separation of the chlorbenzene and benzene.

EXAMPLE 3 When the benzenes of Examples 1 and 2 are replaced with the following aliphatic hydrocarbons and reaction and separation conditions modified slightly, results substantially the same as those of Examples 1 and 2 are obtained: (a) n-butane, (b) n-octane, (c) n-dodecane.

While the present invention has been described primarily with regard to the foregoing exemplification, it should be understood that the present invention is in no way to be deemed as limited thereto but must be construed as broadly as any or all equivalents thereof.

I claim:

1. In a process for the chlorination of benzene by a reaction of benzene and chlorine in a molar ratio of chlorine to benzene of from 1-2:! at a temperature of from 20 to C., in the presence of an accelerator, the improvement wherein said accelerator consists essentially of sodium sulfide in an amount at least stoichiometrically equivalent to the amount of benzene.

2. The process of claim 1, wherein said reaction is conducted at a temperature of from 40 to 50C.

3. The process of claim 1, wherein said reaction is conducted at a temperature of from 60 to 70C. 

2. The process of claim 1, wherein said reaction is conducted at a temperature of from 40* to 50*C.
 3. The process of claim 1, wherein said reaction is conducted at a temperature of from 60* to 70*C. 